This invention relates to synthetic polymers and to methods for their preparation by an isocyanate polyaddition process. More particularly, it relates to the production of such synthetic polymeric products by the reaction of an oligomeric para-, meta- or di-meta-aminobenzoic acid ester or amide and a polyisocyanate.
The production of polymeric products such as polyurethane elastomers by the diisocyanate polyaddition process has found widespread commercial application and is described in numerous patents and other literature. Typically, the production of an elastomer by the diisocyanate polyaddition process will involve the formulation and curing of a composition comprising a polyol, a diisocyanate and a chain-extending or curing agent. Frequently, the polyol, such as a polyester or polyether polyol having terminal hydroxyl groups and a molecular weight, for example, in the range of 750 to 2000, will be pre-reacted with a diisocyanate to provide an isocyanate-terminated prepolymer which may then be reacted with a chain-extending or curing agent for the production of a polyurethane elastomer.
Various systems have been utilized for the production of polyurethanes from a liquid or semi-liquid state. Notably, the commercial manufacture of polyurethane elastomers has been accomplished by the reaction of a polyol and a toluene diisocyanate (TDI), either in admixture or pre-reacted, and a chain-extending or curing agent such as MOCA, i.e., 4,4'-methylene bis(o-chloroaniline). Similarly, a system based upon a polyol and 4,4'-diphenylmethane diisocyanate (MDI) and a 1,4-butanediol curative has achieved commercial application as an alternative to TDI-MOCA systems for the production of polyurethane elastomers.
The various systems utilized for the production of synthetic polymers may have certain disadvantages with regard to the handling and working of the systems and the properties of the resulting polymeric materials. Thus, for example, the utilization of a MOCA or other diamine curative may necessitate the heating of the reaction components to assure adequate mixing of the curative and to prevent crystallization thereof from the reaction system. The employment of elevated temperatures may, however, increase reactivity and cause premature curing thereby limiting the time available for mixing and handling the desired mixture. Similarly, certain problems are associated with the utilization of 1,4-butanediol curative in, for example, a 1,4-butanediol/MDI system. The curative tends to pick up moisture as the result of exposure to the atmosphere and frequently results in the appearance of bubbles or foaming in the cured polymer. In addition, the resulting polymeric material often exhibits a "cheesy" character, thus, hampering demolding of fabricated pieces. Neither the employment of a TDI/MOCA system nor a 1,4-butanediol/MDI system is especially suited to a hand-mixing operation from the standpoint of pot life, and where the manufacture of cured parts by fabricators utilizing such operations is an important consideration, the employment of such systems may be decidedly disadvantageous.
The polyurethane materials of commerce, in addition to the presence of repeating urethane groups, may contain other groups such as urea, ester, ether, aromatic, amine, biuret or allophanate groups. The number, variation and repeatability of these groups along with the urethane groups will depend upon the active hydrogen-bearing materials reacted with a diisocyanate for production of a polymer. The manner in which these groups are combined will determine to a large extent the major physical properties of the finished polymer. While the utilization of a particular reaction system involving particular reactants will be determined in part by the dictates of major physical properties required in a finished polymer, the convenience and ease of handling and fabrication will likewise be important considerations in the utilization of a particular system for the production of a polymeric material. Accordingly, a system for the production, by a simple and effective isocyanate polyaddition process, of synthetic polymers exhibiting useful physical properties will be especially advantageous.